The invention relates to a connector assembly for printed circuit boards, comprising a first connector part with a first housing of insulating material and having a bottom and two opposite side walls and with male contact elements mounted in the bottom of the housing and arranged in rows and columns and having portions projecting form the bottom of the housing, which projecting portions can be inserted into holes of the corresponding printed circuit boards, and a second connector part with a second housing of insulating material and adapted to be inserted into the first housing with an insertion side and with female contact elements mounted in the housing and arranged in a corresponding manner in rows and columns and having portions projecting from a lower side of the housing, which projection portions can be inserted into holes of the corresponding printed circuit board.
Such a connector assembly is disclosed for example in EP-A-0 446 980. In this known connector assembly the second connector part comprises a plurality of outer conductors each substantially enclosing in circumferential direction at least one female contact element operating as signal contact and each contacting the adjacent ground contacts of the corresponding signal contact of the first connector part. In this manner a correct signal transmission can be obtained also at high bit rates of the signals to be transmitted. Further, outer conductors can also be provided in this known connector assembly for the male contact elements operating as signal contacts. Although an optimal signal transmission can be realized with this known connector assembly also at high bit rates, the construction is less suitable for applications, wherein the signal contacts must be very closely spaced one from the other.